Semiconductor diodes have such characteristics that when voltage is forward biased, they allow electric currents to pass through, and when the voltage is reverse biased, they do not allow the currents to pass through. Semiconductor diodes are widely used in various types of electronic circuits such as power supply circuits, signal processing circuits and so on. For a particular type of diode, a forward current is substantially negligible until a forward voltage drop reaches a certain value. For example, silicon p-n junction diodes have a forward voltage drop of at least around 0.7 V. The forward voltage drop of many silicon Schottky barrier diodes can be 0.4 V or even lower owing to Schottky barrier characteristics. The forward voltage drop of germanium p-n junction diodes is about 0.3 V, but their manufacturing process is not compatible with silicon process, and they are very sensitive to temperature, so they are not widely applied. In order to improve the rectification efficiency of a circuit, it is of great significant to reduce the forward voltage drop of a diode as far as possible.
In practical applications, the diode works not only in a current-conducting state, but also in a current-blocking state. Reverse leakage may appears on a current-blocking diode. The leakage will increase circuit loss, reduce circuit conversion efficiency, especially in high temperature applications. Therefore, it is desired that the diode has not only a low forward voltage drop, but also a low reverse leakage.
In many applications, there are inductors in the electronic circuits. Reverse voltage generated by the inductors may be applied to a diode, leading to an avalanche breakdown of the diode. Usually avalanche ruggedness is used to characterize the maximum energy that the device can absorb from the inductor without failing, which is a parameter depending on the size of a junction area for energy dissipation of the device.